Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 6 of 6 Posts

·
Registered
2003 olds bravada
Joined
·
12 Posts
Discussion Starter · #1 ·
Hi folks - I'm new here and although I am a Bravada owner I was hoping for some insight from the knowledgeable folks here even though I don't quite fit in :)

I have an 03 Bravada AWD with the V-6 (120K miles). Power has been greatly diminished of late and shifting has been odd. I took it to a shop (non dealer) and they said the engine was running "lean" and that the Cat was fouled and needed to be replaced in order to further troubleshoot why the engine was running lean. Their estimate just to replace the Cat was $450 for the part and another $150 for labor (plus tax and shop fees). Unfortunately unlike many here I do not have the talent to do this work myself. So any ideas on what might be the problem besides the cat? And any recommendations on how/where to have this work done cheaper since I've seen much cheaper prices when searching for Cat here? I am in the Kansas City area in case folks here have local recommendations.
 

·
Registered
2003 chevy trailblazer_lt_ext
Joined
·
967 Posts
A bad CAT is possible. However there are a lot of other things that can cause loss of power. Are you getting an SES light? Did they tell you if there was any codes? If so, do you know what the codes are? If not, you can take it to most auto parts stores and they will read them for free. Without the codes, all we can do is guess. Some easy and cheap things to do that might help: clean the throttle body, change the fuel filter, run fuel injector cleaner through it for a couple of rounds of a full tank of gas, change the air filter, and look for vacuum leaks, especially under the air box.

Welcome! And don't forget to fill out your profile so we can see what you have and be in a better position to help you. Oh, and its an I6 (inline), not a "V"6.
 

·
Registered
2003 olds bravada
Joined
·
12 Posts
Discussion Starter · #3 ·
Thanks Doc!

All very good questions and yes I will update my profile with my specifics and fix the I6 engine reference :)

There was no engine light and no code. The TB was cleaned 3 months ago and was re-checked and its clean. The shop did say quite clearly that the Cat is very clogged from inspection and because of that (and with no other codes) that they couldnt get any clear readings on other problems. So their statement was to replace the Cat and then do further troubleshooting. I unfortunately have put a lot of money in this vehicle in the past 2 years and am reluctant to continue doing so especially when they don't know what is wrong. Spending close to $700 to find out I have another $X problem to fix is a tough pill to swallow.

Anyway thats what I know so far - thanks for your help :0

- Candide
'03 Bravada AWD I-6 engine
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
997 Posts
If the cat is clogged, it can cause the symptoms you describe, but one must ask why the cat got clogged in the first place. Usually it's a misfire that goes unattended. (The SES flashes, which means to stop NOW, but maybe the previous owner ignored it. Misfires can then go away, but it leaves permanent damage to the cat.) Cats are designed to last the life of the vehicle if the vehicle is maintained properly.

One common cause of misfires is spark plugs. Our trucks do not like Bosch plugs; only the AC Delco iridium plug works well. (Others have reported good results from the NGK iridium.)

Another cause of misfires is a bad coil.

The first thing to do is to find out if the cat really is clogged. I have no reason to doubt your mechanic's diagnosis, but if you want a second opinion, any good muffler shop can simply put a vacuum/pressure gauge in the hole for the upstream oxygen sensor and measure the exhaust backpressure. At idle, it should be close to 0. At higher RPMs, it can go as high as 1 to 2 psi, but a clogged cat will register 4 or more psi.

If the cat is clogged, start looking for the reason why. Check the plugs, and if there is more than 100,000 miles on them, replace them with new AC Delco iridium plugs. If there is any other brand plug besides AC Delco, replace them anyway.

Changing plugs is something you can easily do in your driveway. (There are lots of threads in here on it.) Be thankful you don't actually have a V6, because many of them required a LOT of work to swap plugs.

Let us know how it works.

As for the price, there are 'universal' cats that cost less, but they require fitting and welding. OEM cats are quite pricey. But if your cat is clogged like they say, you have no choice; it will only get worse.
 

·
Registered
2003 olds bravada
Joined
·
12 Posts
Discussion Starter · #5 ·
Thanks Chickenhawk! I appreciate your reply and I'll comment where I can. You ask why the cat was clogged in the first place and this is indeed what my shop is asking. Unfortunately they can't figure that out until I replace it.

I am the original owner of this vehicle and I have had all recommended preventative maintenance performed (through the 100K service) through a GM dealer. This included the 100K service which was as I am sure you know thorough AND expensive. I can only assume plugs were changed at that time with AC Delco plugs (since it was a dealer). I have seen no engine lights or noticed any misfires (that I am aware of) and when I have seen engine lights I have had them analyzed and fixed (fan clutch being a recent culprit). So I do maintain my vehicles as scheduled.

Its only been since moving past 100K that I have tried other service outlets partially for price and partially for convenience.

Anyway I am debating fixing and hoping for the best when they find out the culprit behind the problem.

- Candide
03 bravada awd I-6
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
997 Posts
Keep us informed. Undiagnosed problems can be discouraging, but once it is all worked out, you will still have a good, solid and reliable vehicle.

There is no question that cats that are supposed to last the life of the vehicle fail prematurely in a lot of cases. Once the cat is replaced, I would also talk to your mechanic about a new upstream oxygen sensor. They can go gradually bad; enough to effect performance but not enough to illuminate the SES light.

Most of us in here routinely replace the oxygen sensor at the 100,000 mile service when the plugs are done too. (Check your work order from the dealer for that 100,000 mile service - they may have already replaced it.)
 
1 - 6 of 6 Posts
Top